The present invention relates to a horizontal electric field type liquid crystal display (LCD) and a manufacturing method thereof.
Liquid crystal displays (LCDs) belong to a primary type of flat panel display (FPD).
According to the orientation of the electric field for driving liquid crystal, a LCD can be classified as a vertical electric field type LCD and a horizontal electric field type LCD. The vertical electric field type LCD comprises a Twist Nematic (TN) type LCD; the horizontal electric field type LCD comprises a Fringe Field Switching (FFS) type LCD and an In-Plane Switching (IPS) type LCD.
In an LCD, generally, storage capacitance can be formed between the pixel electrode and the common electrode, and parasitic capacitance can be formed between the pixel electrode and the data line. The storage capacitance is used for aligning liquid crystal so as to display image; the parasitic capacitance is a kind of interference capacitance, disturbing the normal alignment of liquid crystal. Therefore, during the manufacturing of a LCD, the pixel electrode and the gate line may be spaced from each other in order to prevent the undesirable phenomenon caused by the parasitic capacitance. But, this causes the increase of the shielded area by black matrix and the decrease of aperture ratio of the LCD. Aperture ratio is one of the main indexes for evaluating LCD; and in general, the higher the aperture ratio, the better the LCD.
One existing technique for improving aperture ratio comprises: coating a thick organic insulating layer between the pixel electrode and the data line, thus reducing the interference of the parasitic capacitance by increasing the straight line distance between the pixel electrode and the data line. That is, the method includes forming the organic insulating film on the substrate after forming the data line, and then forming the pixel electrode on the organic insulating film. The aperture ratio can be increased by about 30% through this method of inserting an organic insulating film.
Another existing technique for improving aperture ratio comprises a method of forming color resins on an array substrate.
Wide viewing angle is another one of the main indexes for evaluating a LCD. The horizontal electric field LCD is one of the widely used techniques for realizing wide viewing angle.
FIG. 1 is a sectional schematic view of an existing horizontal electric field LCD. As shown in FIG. 1, the LCD comprises a first substrate 11 and a second substrate 21. A common electrode 13 is provided on the first substrate 11, a gate electrode 12 is provided at a side of the common electrode 13, a gate insulating layer 14 covers the gate electrode 12 and the common electrode 13, a semiconductor layer 15 is provided over the gate electrode 12, a drain electrode (data line) 16 is provided on the semiconductor layer 15, a passivation layer 17 covers the whole substrate, and a pixel electrode 18 is formed on the passivation layer 17 and electrically connected to the data line via a through hole in the passivation layer 17.
Here, the horizontal electric field LCD forms the horizontal electric field by forming a pixel electrode and a common electrode on the first substrate, and controls alignment of liquid crystal within the horizontal plane by forming a horizontal electric field, thus to realize better performance of wide viewing angle.
Since the structure of the horizontal electric field LCD is different from that of a vertical electric field LCD, the above two techniques for improving aperture ratio can not be utilized.
In particular, if the first technique for improving aperture ratio is used in a horizontal electric field LCD, the straight line distance between the pixel electrode and the common electrode becomes greater and so the horizontal electric field can not be formed effectively. If the second technique for improving aperture ratio is used in a horizontal electric field LCD, the color resins are located within the horizontal electric field area while the liquid crystal are out of the horizontal electric field. Therefore, even if the horizontal electric field is formed, the electric field can not be used to effectively align the liquid crystal.